An instance is not a replacement for groups, and it's most definitely not similar to a Reddit community. What you want is, well, "groups" which is a feature th

An instance is not a replacement for groups, and it's most definitely not similar to a Reddit community. What you want is, well, "groups" which is a feature that GNU Social had, and which is eventually going to come to Mastodon and Pleroma. A lot of people seem to happily use Twitter which also doesn't have a concept of groups.